From db70fdefc77715c2a36c145ce6f2ab25a2d052a2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Sun, 31 May 2026 13:02:45 +0200
Subject: [PATCH 1/2] add tests

---
 test/testunusedvar.cpp | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/test/testunusedvar.cpp b/test/testunusedvar.cpp
index ae44305ef6a..e2c2f0d6715 100644
--- a/test/testunusedvar.cpp
+++ b/test/testunusedvar.cpp
@@ -80,6 +80,7 @@ class TestUnusedVar : public TestFixture {
         TEST_CASE(structmember32); // #14483
         TEST_CASE(structmember33);
         TEST_CASE(structmember34);
+        TEST_CASE(structmember35);
         TEST_CASE(structmember_macro);
         TEST_CASE(structmember_template_argument); // #13887 - do not report that member used in template argument is unused
         TEST_CASE(classmember);
@@ -2101,6 +2102,16 @@ class TestUnusedVar : public TestFixture {
         ASSERT_EQUALS("[test.cpp:2:24]: (style) struct member 'S::p' is never used. [unusedStructMember]\n", errout_str());
     }
 
+    void structmember35() {
+        checkStructMemberUsage("struct S { int i; };\n"
+                               "int f() { return g<S>(); }\n");
+        ASSERT_EQUALS("", errout_str());
+
+        checkStructMemberUsage("struct S { int i; };\n"
+                               "int f() { A<S> *a = nullptr; (void) a; }\n");
+        ASSERT_EQUALS("", errout_str());
+    }
+
     void structmember_macro() {
         checkStructMemberUsageP("#define S(n) struct n { int a, b, c; };\n"
                                 "S(unused);\n");

From 9a4e24dbe805e12743c711a368880e4a57adf778 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ludvig=20Gunne=20Lindstr=C3=B6m?=
 <ludviggunnelindstrom@gmail.com>
Date: Sun, 31 May 2026 12:59:04 +0200
Subject: [PATCH 2/2] fix

---
 lib/checkunusedvar.cpp | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/lib/checkunusedvar.cpp b/lib/checkunusedvar.cpp
index dd30f65db58..17b3e445cbd 100644
--- a/lib/checkunusedvar.cpp
+++ b/lib/checkunusedvar.cpp
@@ -1680,6 +1680,29 @@ void CheckUnusedVarImpl::checkStructMemberUsage()
                     if (use)
                         break;
                 }
+                // Class used in template with unknown definition
+                if (Token::Match(tok, "%name% <") && tok->linkAt(1)) {
+                    if (tok->function())
+                        continue;
+                    if (tok->type() && tok->type()->classScope)
+                        continue;
+                    {
+                        const Token *start = tok;
+                        while (Token::Match(start->previous(), "%name%|::"))
+                            start = start->previous();
+                        if (mSettings.library.detectContainer(start))
+                            continue;
+                    }
+                    const Token *end = tok->linkAt(1);
+                    for (; tok != end; tok = tok->next()) {
+                        if (tok->type() && tok->type()->classScope == &scope) {
+                            use = true;
+                            break;
+                        }
+                    }
+                    if (use)
+                        break;
+                }
                 if (tok->variable() != &var)
                     continue;
                 if (tok != var.nameToken()) {